When soil is at liquid limit, Ic = .............. | Civil MCQ | Examoogle

Examoogle • User • info@examoogle.com • EE-2024-8821

Chapter 1 of 12 • Page 1 of 248🔒 Protected PDF • Watermarked

Back to Practice Questions

CivilSoil Mechanics

Prev Next

When soil is at liquid limit, Ic = ..............

infinity

none of these

Correct Answer

⚙️ TE • Technical Concept & PrincipleCivilSoil Mechanics

Option A

Quick Summary:

The Consistency Index ( $I_c$ ) is a measure of the relative stiffness of a fine-grained soil. By definition, when the natural water content ( $w_n$ ) of a soil is equal to its liquid limit ( $w_L$ ), the consistency index becomes zero.

⚙️TETechnical SolutionConcept & Principle

💡 Explanation

🔢 Key Formulas

$I_c = \frac{w_L - w_n}{I_p}$ — Consistency Index formula

$I_p = w_L - w_P$ — Plasticity Index formula

⚙️ Working Principle

The consistency index is defined as the ratio of the difference between the liquid limit and the natural water content to the plasticity index of the soil. When $w_n = w_L$ , the numerator becomes zero, resulting in $I_c = 0$ . This indicates that the soil is in a liquid state, having minimal shear strength.

📌 Key Points

▸
Consistency index describes the state of cohesive soil relative to its liquid and plastic limits.
▸
If $I_c = 1$ , the natural water content is equal to the plastic limit ( $w_n = w_P$ ).
▸
If $I_c > 1$ , the soil is in a semi-solid or solid state.
▸
If $I_c < 0$ , the soil is in a liquid state ( $w_n > w_L$ ).

✅ Advantages

▸
Provides a quick assessment of soil consistency in the field.
▸
Useful for evaluating the engineering behavior of clays.

❌ Disadvantages / Limitations

▸
Limited to fine-grained soils (clays and silts).
▸
Does not account for soil structure or sensitivity.

🛠️ Applications / Uses

▸
Foundation engineering design.
▸
Predicting settlement characteristics of clayey deposits.

📄 Additional Information

▸
The consistency index is different from the Liquidity Index ( $I_L$ ). $I_c + I_L = 1$ .
▸
Option B ( $I_c=1$ ) corresponds to the plastic limit, not the liquid limit.

📊 Diagram / Illustration

✅

A is correct — The consistency index $I_c$ is calculated as $(w_L - w_n) / I_p$ ; therefore, when $w_n = w_L$ , $I_c$ equals 0.

Core Concepts Used

Click any tag to open in AI Tutor

Atterberg Limits Consistency of Soil Soil Mechanics

💡 EXAM TIP

Always verify if the question asks for Consistency Index ( $I_c$ ) or Liquidity Index ( $I_L$ ), as their definitions are inverse at the Atterberg limits.

Discussion (0)

Loading discussion...

Prev Next

Correct Answer

Related Questions

Discussion (0)